1. Field of the Invention
The present invention relates to an azimuth calculation apparatus which includes an azimuth sensor mounted on a moving body such as an automotive vehicle for detecting a direction of the moving body relative to the earth's magnetism.
2. Description of the Prior Art
U.S. Pat. Nos. 4,413,424 and 4,416,067 respectively issued on Nov. 8 and 22, 1983, disclose a conventional azimuth sensor which is constructed with an excitation winding wound on an annular ferromagnetic core and a pair of output windings wound on the core perpendicularly relative to one another. In a condition where such an azimuth sensor is mounted on a moving body, an azimuth circle is determined by outputs of the output windings in a circular locus given by one rotation of the moving body. When a temperature of the azimuth sensor changes in a demagnetized condition of the moving body, the azimuth circle changes in diameter but does not change in its center. For this reason, the direction of the moving body can be detected on a basis of outputs from the azimuth sensor without causing any error. It has been, however, found that when a temperature of the azimuth sensor changes in a magnetized condition of the moving body, the azimuth circle changes in diameter and further changes in its center. This causes an error in calculation of the direction of the moving body based on the outputs from the azimuth sensor.